Abstract
Introduction
Adipose stem cells (ASCs) have shown therapeutic promise for inflammatory conditions that beget multi organ dysfunction, including burns. While ASCs have immunomodulatory properties, some studies have brought up safety concerns of increased pro-coagulant activity such as pulmonary microvascular thrombi formation after intravenous (IV) administration of ASCs. In the present study, the aims are two-fold: 1) to verify if IV administration of human ASCs promotes coagulation and 2) to determine if human ASCs affect organ function in a 40% total body surface area (TBSA) swine burn model.
Methods
Female Yorkshire swine (39.63 ± 8.26kg) were anesthetized and subjected to 40% TBSA full thickness contact burns according to a formerly established model. After recovery from anesthesia, animals were randomized to receive 15ml/kg Lactated Ringer’s Solution containing: 1- no ASCs; 2- a low dose (5x105 ASCs/kg), or 3- a high dose (5x106 ASCs/kg) over a 15-minute period as a bolus. Blood was collected at baseline (BL) and 3, 6, 12, and 24h post burn to determine the effect of ASCs on organ function and coagulation status. At 24h post-burn, animals were humanely euthanized, and kidney and liver tissue was collected for histological and Western blot analyses. Data is presented as mean ± SEM, and statistical significance was set at p< 0.05.
Results
The high dose of ASCs significantly increased the circulating number of monocytes starting at 12 hours. Two-way ANOVA revealed a significant effect of ASCs on both prothrombin times (PT) and international normalized ratio (INR) (1.03 ± 0.04, 0.93 ± 0.03, and 1.02 ± 0.04 for no, low and high ASC groups, respectively at 24 hours). There were no differences in partial thromboplastin time, fibrinogen, or d-dimer levels. Both doses of ASCs briefly exacerbated burn-induced increases in total bilirubin at 3 hours (0.062 ± 0.025mg/dL, 0.148 ± 0.060mg/dL, and 0.211 ± 0.086mg/dL in no, low, and high ASC groups, respectively). ASCs did not alter urine output; yet, there was a significant effect of ASCs on creatinine. Western blotting revealed a rise in caspase expression in the liver of animals receiving a low dose of ASCs, while there was no difference in caspase expression in kidneys.
Conclusions
We show that IV administration of xenogeneic ASCs produces minimal changes in coagulation status and renal and hepatic dysfunction. Modest changes in the extrinsic coagulation pathway were dose-dependent, while exacerbation of liver dysfunction was brief and normalized after administration of ASCs was completed. We cannot rule out that continuous infusion of ASCs would not have a cumulative effect on organ dysfunction.
Low-dose strontium stimulates osteogenesis but high-dose doses cause apoptosis in human adipose-derived stem cells via regulation of the ERK1/2 signaling pathway
